Moscow Polytechnic University, Moscow, Russia

S. A. Tipalin, Cand. Eng., Prof., Dept. of Material Forming and Additive Technologies, e-mail: tsa_mami@mail.ru
D. A. Gnevashev, Cand. Eng., Associate Prof., Dept. of Material Forming and Additive Technologies, e-mail: dengnevashev@mail.ru
N. D. Borisov, Postgraduate Student, Dept. of Material Forming and Additive Technologies
M. V. Bodnar, Postgraduate Student, Dept. of Material Forming and Additive Technologies
V. A. Klimov, Postgraduate Student, Dept. of Material Forming and Additive Technologies

Abstract: This article analyzes the effect of as-delivered thickness of 20 grade cold-rolled steel on mechanical properties and hardening characteristics of the material. Specimens subjected to uniaxial tension demonstrated the dependence of tensile strength, yield strength, and ultimate tensile failure strain on the material thickness. Experiments have shown that, as the material thickness decreases, tensile strength and ductility decrease. The change in tensile strength in the thickness range from 1 to 3 mm varies insignificantly and is in the range of 612-645 N/mm². With a thickness reduction to 0.5 mm, the yield strength decreases to 461 N/mm2. A decrease in the tensile failure strain of the specimen from 0.64 to 0.41 also occurs with a decrease in the sheet material thickness. The greatest change occurs with the transition from a thickness of 1.0 mm to 0.5 mm. In this range, the ultimate failure strain decreases from 0.55 to 0.41. The yield strength changes insignificantly and increases with decreasing sheet thickness. It was found that the exponent of the hardening curve increases from 0.38 to 0.46 with increasing material thickness from 0.5 to 3.0 mm, while the hardening coefficient decreases from 797 to 754 N/mm². Determining the change in the nature of the hardening curve coefficients with material thickness allows for the calculation of intermediate values for thicknesses from 0.5 to 3.0 mm, which can improve the accuracy of calculations in computer modeling of stamping processes. The nature of hardness changes with material thickness was also determined. Microhardness measurements in crosssections of sheet material revealed a decrease in hardness with increasing specimen thickness. Hardness changes were in the HV range from 182 to 170 N/mm².

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